In our household, teething is the universal solvent: Whatever the problem with the baby, the cause is teething. Since almost all problems in infancy need to be worried about less, not more, this is ideal: All we need is an explanation, not the explanation.

But for many centuries, teething was not a reassuring explanation. It was the opposite. The irritation of the gums, the failure of the teeth to break through—all this was said to upset the fragile nervous system of the child, causing severe convulsions and quite possibly death. The etiology was somewhat unclear, but the consequences were not. They had been clear since Hippocrates, who wrote about it. In 19th-century England, more than 10 percent of childhood deaths were blamed on teething. Even as late as 1894, you could find doctors in the U.S. writing sentences like this: “So deadly has it become, that one-third of the human family die before the twenty deciduous teeth have fully appeared.”

All this had a certain logic. In an age of high infant mortality, it made sense to blame that mortality on the proximate cause—the misery that the infant was clearly experiencing. But attributing all maladies to teething was not benign. The treatment—often lancing, often less than sterile—could be fatal. (It was only at the turn of the 20th century that medical opinion turned against slicing open the gums: “Lancing the gums … has lost most of its charms,” the pediatrician Abraham Jacobi memorably wrote in 1903.) In 1860, an American doctor, fed up with all this, wrote angrily, “I can assure you that the readiness to attribute all the diseases of infantile life to teething has destroyed more human beings than many of the wars described in history.”

To ward off the curse of teething, babies since ancient times have worn necklaces adorned with magical charms: coral sticks, semiprecious stones, a wolf’s tooth. Some amulets were designed for dual use as chew toys, but many were not. Sometimes they were even tied around the waist, not the neck. They were meant not for the body but the spirits.

There are few things that have inspired as many folk remedies as teething: The lists of remedies go on and on. And they live forever. In ancient Greece, Soranus recommended rubbing the brains of a hare on the gums. You can find this same treatment in recent American folklore. (Also, from Tennessee: Rub a minnow on the gums.)

In the 1800s, there were fewer topical applications of brains and more proprietary concoctions. Teething was now big business. Numerous solutions and syrups were trumpeted, and in this lightly regulated era, many households were awash, unknowingly, in drugs. Many parents swore by Mrs. Winslow’s Soothing Syrup, for example, whose advertisements proclaimed, “Depend on it, Mothers, it will give rest to yourselves and relief and health to your babies.” It gave rest but not health: It was, essentially, “a cocktail of morphine and alcohol.”

I am not very different from any of these parents, of course. I attribute all maladies to teething too. But I am saved from the consequences of my folk explanations: No one is willing to lance anything anymore. If teething once meant everything, it is now said to mean nothing: The current medical literature stresses its deep insignificance. Even everything you have been told teething causes—diarrhea, high fevers, agitated sleep—doctors will be happy to tell you that teething does not cause. In the words of one physician, and in violation of millennia of superstition and scientific conviction: “Teething produces nothing but teeth.”

Fellow parents! Are you at a loss as to how to encourage your child to use the potty? Have you had enough of the Cheer for Me Potty and Where’s the Poop? Perhaps the problem is that you have not read The Care and Feeding of Infants, by Frederic H. Bartlett. You should be ashamed. But it is never too late.

If you can, start training your infant to have a bowel movement in the chamber each morning at the age of one month. ... Place the chamber on your lap … and hold the infant over it. ... Insert about two inches into the rectum, a tapered soap stick, keep it there from 3 to 5 minutes... The movement will usually occur under this stimulus. If you keep this up with regularity, a daily bowel movement will probably result.

Probably!

The Care and Feeding of Infants was published in 1932. In the previous few decades, child rearing, as dictated by experts, had gone from indulgence and sentimentality to a task that should be conducted without mercy. Babies should no longer be babied; they should be bent to parental will. And the sphincter of the infant was not exempt. It was as important as anything else, if not more.

The change happened in a hurry. The 1914 edition of Infant Care, the U.S. Children’s Bureau guide to child care, recommended that toilet training begin by the third month, but mothers were told that making their baby tense would make matters worse. They should be gentle and laugh, and they should not scold. Their child should be relaxed, for obvious reasons. By 1921, though, there was no more laughter, and there was no more talk of relaxation. In their place, there was rigor and firmness and discipline. Behaviorism, the idea that everything in infancy can be mechanically learned, was ascendant.

But within less than 20 years, incredibly enough, the conventional wisdom would shift yet again, this time under the influence of Freudianism. According to this interpretation, babies were said to take deep sensual pleasure in vacating their bowels, and parents who toilet-trained too early were inhibiting the ability of their children to experience pleasure. Right now you are saying, but bowel movements make my baby miserable. Yes. As with much midcentury Freudian child-rearing advice, a little experience at home actually caring for babies would have cleared up a lot of confusion.

But never mind that: Too-early toilet training posed the risk of permanent lifelong damage. “In extreme cases,” according a 1947 book, “one becomes parsimonious, stingy, meticulous, punctual, tied down with petty self-restraints. Everything that is free, uncontrolled, spontaneous is dangerous.” The anthropologist Geoffrey Gorer freely attributed the Japanese character to the early toilet training of Japanese infants—apparently forgetting that many American infants had been trained in much the same way only a couple of decades earlier.

Such whiplash-like reversals, of course, never end, as even in recent years very early toilet-training has come, once again, in vogue. A rare source of sanity is the education professor Celia Stendler, who in 1950 surveyed the previous 60 years of wildly vacillating child-rearing advice in women’s magazines. Instead of pounding in her head with a soap stick, she somehow emerged with among the wisest words ever written about caring for baby. Her language is filtered through midcentury Freudianism, but it is no less moving for it.

“What we can do,” she concluded, “what certainly needs to be done, is to help parents develop insight into their own personalities in the hope that they can more intelligently approach problems of child rearing. No trend in this direction has been noted in the literature examined.”

A doctor shows a group of Chinese parents how to help their babies exercise as they take part in an activity to celebrate the upcoming International Children's Day, in Beijing on May, 2010.

Photo by Stringer/AFP/Getty Images

The small humans of America are the most razzle-dazzled, overstimulated, bugged-out small humans in the world. (Survey says.) It’s not working out so well. I suggest we shift our focus: from cognitive development to motor. And at least in the short-term, I guarantee results.

Evidence from around the world shows that early work in motor development actually has effects. Kipsigis infants in Kenya are famously trained to sit by being placed in muscle-stressing dugout holes. Nso babies in Cameroon are taught to walk, toddling along poles for balance. Practice makes perfect: The Kipsigis sit up earlier than we do; the Nso walk earlier. (The psychologist Philip Zelazo ran roughly the same experiment on his own son. It worked.)

We cannot prod our children toward genius. But we can prod them toward seriously precocious roller-skating. That’s not nothing.

A little less than a century ago, this country was riveted by the spectacle of Jimmy and Johnny Woods, twins who were from birth the subject of a very simple experiment: What would happen if you gave Johnny massive amounts of physical stimulation, if you treated him like a future Olympian—and if you treated Jimmy like a normal kid? The project of the psychologist Myrtle McGraw, it was sensationally successful almost immediately. Johnny swam underwater at 9 months. He roller-skated at 12 months. Just shy of 14 months, he dove headfirst into a pool. At 15 months, he swam 20 feet with his head in the water. It was all captured on film. Time magazine covered it.

Against the all-or-nothing perspectives of the time—neural maturation is all; no, learning is all—McGraw favored complexity. She thought that neural maturation and learning both mattered. They interacted. Before a baby would get around to something on his own, his environment—a team of relentless psychologists, or a dug-out hole—can inspire it.

Johnny’s training, five days a week for two years, was intense. Then the workouts stopped. By the time the twins were 6, Jimmy had pretty much caught up. Johnny was still more coordinated, though, and more confident. All those months at the gym had paid off.

If you are not willing to consign your child to an infancy spent at LA Fitness, there is a slack-ass option: Spin her in an office chair. In what may be the most entertaining experiment in the developmental literature, babies who are spun in a chair—20 times twice a week, for a month—score higher on later motor development measures than babies who are not. It only looks like silliness. It is actually vestibular simulation.

This is my contribution to overstimulated, passive-aggressive, hyper-anxious American parenting: If you really love your child—if you want to give her a head start in life—then twirl her around without mercy.

New parenthood is a desperate search for certainty: When you start knowing nothing, you are desperate to know something. And when you finally figure that something out—how to get this creature to eat or sleep—that becomes the answer. Any parent this side of sanity clings to that certainty for dear life.

Sara Harkness, a professor of human development at the University of Connecticut, has spent decades compiling and analyzing theanswers of parents in other cultures. They have a lot of answers, it turns out. And they are very certain about those answers. To read her work and the work of her colleague and husband, Charles Super, is to be disabused of a lot of certainties about child rearing. For the anxious, easily unsettled parent, it should be followed by a chaser of Brazelton and Karp, just to restore your world to its locked and upright position.

It’s not a shock that child care varies across cultures, of course. But it is still hard to comprehend just how many ways there are of looking at a baby. I have been reading various ethnographic works on child rearing for years now, and yet, when I talked to Harkness last week, I started by asking her what child-rearing practices vary most among cultures. This is a worthless question. All child-rearing practices vary hugely among cultures. There’s only a single shared characteristic, Harkness says: “Parents everywhere love their children and want the best for their children.” (Even this is a controversial statement; some academics would argue otherwise.) Everything else, including the way in which they love their children and what the best might mean, is subject to variation.

I am not talking about National Geographic bare-breasted, hunter-gatherer pictorials. Those are the most memorable variations in child care, the sort we can see: Think of the live-in Mongolian livestock in Babies. What makes the work of Harkness so interesting is that it highlights the variations we are unable to see. Even when compared to other Western cultures, we Americans are a deeply strange people.

Every society has what it intuitively believes to be the right way to raise a child, what Harkness calls parental ethnotheories. (It is your mother-in-law, enlarged to the size of a country.) These are the choices we make without realizing that we’re making choices. Not surprisingly, it is almost impossible to see your own parental ethnotheory: As I write in Baby Meets World, when you’re under water, you can’t tell that you’re wet.

But ethnotheories are distinct enough, at least to an outsider, that they are apparent in the smallest details. If you look just at the words parents use to describe their children, you can almost always predict where you are in the world. In other words, your most personal observations of your child are actually cultural constructions. In a study conducted by Harkness and her international colleagues, American parents talked about their children as intelligent and even as “cognitively advanced.” (Also: rebellious.) Italian parents, though, very rarely praised their children for being intelligent. Instead, they were even-tempered and “simpatico.” So although both the Americans and the Italians noted that their children asked lots of questions, they meant very different things by it: For the Americans, it was a sign of intelligence; for the Italians, it was a sign of socio-emotional competence. The observation was the same; the interpretation was radically different.

Every society interprets its children in its own way: The Dutch, for example, liked to talk about long attention spans and “regularity,” or routine and rest. (In the Dutch mind, asking lots of questions is a negative attribute: It means the child is too dependent.) The Spanish talked about character and sociality, the Swedes about security and happiness. And the Americans talked a lot about intelligence. Intelligence is Americans’ answer. In various studies, American parents are always seen trying to make the most of every moment—to give their children a developmental boost. From deep inside the belly of American parenthood, this is so obvious it isn’t even an observation. It is only by looking at other societies that you can see just how anomalous such a focus is.

Looking back at her research, Harkness can trace the history of how we got this way. During interviews with middle-class Boston parents in the 1980s, she and her colleagues kept hearing about the importance of “special time” or “quality time”: One-on-one time that stimulated the child and that revolved around his interests. Nearly every American parent mentioned it, she says. “It was this essential thing that all parents seemed to think they should do—and maybe they weren’t doing enough of it.”

This seems obviously reasonable. I would likely say “special time” with ironic quotation marks, but I still feel pretty much the same way those parents did. How else would a halfway-decent parent feel? But when Harkness talked to other halfway-decent parents in other cultures, even other seemingly very similar Western cultures, they were oblivious to this nagging feeling. Harkness recalls that “in the Netherlands, a father said, ‘Well, on Saturday mornings, my wife sleeps late, I get up with the kids, and I take them to recycle the bottles and cans at the supermarket.’ ” That was their special, stimulating, child-directed time: recycling bottles and cans. Asked if an activity was developmentally meaningful, the Dutch parents would brush off the question as irrelevant or even nonsensical. Why think of every activity as having a developmental purpose?

What you notice reading these accounts is how much more intensive—how much more arousing—American parenting is. Harkness has characterized it as trying “to push stimulation to the maximum without going over the edge into dysregulation of basic state control.” This is true even if you think you’re different—that you’re not like those other parents at the playground. Culture operates at a deeper level than any individual parenting choice. In a survey Harkness and her colleagues conducted of parents in Western cultures, the last question was, “What’s the most important thing you can do for your child’s development right now?” “The American parents almost to a person said, ‘Stimulation—stimulation is what my child needs.’ Interestingly, even the attachment parents, who were very adamant about being different in a lot of ways—they still gave the same answer.” And all the parents meant a very particular sort of stimulation. The parents talked about themselves in almost curatorial terms: They’d create a setting for intellectual growth. It went almost without saying that the actual stimulation came from the toys.

But ask an Italian mother about stimulation and her thoughts immediately go to her husband: He comes home and makes the baby jump, she told the researchers. “He is the ‘baby skier,’ ” she says, wonderfully. “The ‘baby pilot.’ ” Meanwhile in Spain, everyone—experts, doctors, mothers—stressed the importance of a stimulating daily walk: You see the people in your neighborhood. Objects aren’t stimulating. People are stimulating.

Of course, we have now taken special time and squared it. It’s now translated through the buzz-phrased, consultant-happy language of early cognitive development, with talk of “developmental spurts,” and “brain architecture,” and “maximizing potential,” and “making new connections,” and “pruning synapses.”

All this worries Harkness. “We’re on the verge of trying to export very ethnocentric ideas about what competencies children need to develop at a very early age, which is really unfortunate,” she says. “The U.S.’s almost obsession with cognitive development in the early years overlooks so much else.”

What else? Well, nothing in American parenting is anything like the concept of ng’om, which is used by the Kipsigis people in rural Kenya to describe children who are especially intelligent and responsible. This concept of intelligence, as Harkness and Super have written, highlights “aspects of social competence, including responsibility and helpfulness.” These aspects, they add dryly, “have tended to be overlooked in Western formal theories of children’s intelligence.”

Part of the lesson of parental ethnotheories is that when we look for certain qualities, we stop seeing others. It’s a cruel circle: Because our version of intelligence overlooks ng’om, we don’t prize it. Because we don’t prize it, we don’t see it. Because we don’t see it, we obviously don’t encourage it or acknowledge it—we don’t create its condition for possibility. And yet none of this stops us from wondering, years later, why our children insist on leaving their damn coats on the floor.

Go ahead and laugh! The history of infancy is nothing but a very long, very sincere thread of #BabySlatePitches. For example: “Child sucking his thumb? Don’t let him bend his arm.” A century ago, as I write in Baby Meets World, well-meaning parents were so menaced by thumb-sucking that they strapped stiff splints around the elbows of their children. (They also pinned nightgowns to the mattress.)

But that’s too easy: Parents have been doing misguided things to their children since there were children. The most interesting #BabySlatePitches are the ones that are exonerated: the totally insane stuff that turns out to be surprisingly sensible.

“Give your baby a machete. It’s good practice.”

It’s the sort of sentence that stops you in your tracks: The Aka, a hunter-gatherer people in central Africa, teach “their eight-to- twelve-month-old infants how to use small pointed digging sticks, throw small spears, use miniature axes with sharp metal blades.”

This is not a hoax. It isn’t even that unusual. Once the infants of Fore people in New Guinea begin to walk, they are taught how to handle knives. Babies among the Efe, who live in the Congolese rainforest, are said to “routinely use machetes safely.”

None of these people share our foam-padded, toilet-locked lifestyle. Both the Aka and the Efe are subsistence societies. Survival is never a given. They teach their babies to use machetes in part because they need the help: Children are supposed to be useful from a shockingly young age. See this photo of an 11-month-old Efe infant carefully cutting a fruit in a half with a machete.

These machete-wielding babies do strikingly well: In the ethnographic record, there are no accounts of parents or siblings being hacked to pieces. Which is not to say that a machete is a good first birthday present for the hard-to-buy-for baby, even if he’s interested in cooking with Dad: For one thing, Babies R Us doesn’t carry any.

“Two enemas a day keep the doctor away.”

There’s pooping in the bath by accident and there’s pooping in the bath on purpose. And then there’s pooping in the bath because your parents made you do it: The Beng people of West Africa give their babies twice-daily enemas. Yes: enemas. Starting when the cord stump falls off.

This sounds like a truly disastrous idea. The Beng are chronically malnourished, and enemas are a good way to end up even more malnourished. (And they are excruciatingly painful for the baby.)

But enemas are not an optional part of Beng culture. They cannot be excised by a well-meaning NGO. Because Beng mothers go back to work in the fields a few months after birth, they depend on allomothers, often young girls, to watch their babies during the day. But no one wants to watch a child who’s going to defecate on you. (The Beng use no diapers at all. Plus, their taboo against excrement is even stronger than our own—it is considered morally dirty.) The enemas solve this problem: They make the baby regular. By the time a Beng mother returns to work, her baby, somewhat astonishingly, should only defecate during bathtime.

In a way, the whole structure of Beng life rotates around enemas: no enemas, no childcare, no mothers working, no farming. No Beng.

No one has worse manners than babies. They will not stop with the staring.

Fresh from the womb, we like to look at faces. An infant minutes old turns toward faces. We seem to sense that they’re important. But we also like to look at things that resemble faces—if something is facelike, that’s enough to attract a newborn’s attention. At birth, we are what scientists call “broadly tuned” to faces. We don’t discriminate finely; if something looks like it might be a face, we take it seriously. A Richard Nixon mask would be enough. (There’s no data on that, though.)

We’re so broadly tuned, in fact, that our antennae for faces isn’t human-specific: Newborns don’t prefer the faces of their own species over those of another primate. Without even having taken an introductory course in evolution, we see nonhuman primates as being a lot like us. And there’s more: At 6 months, babies are as good at telling apart monkeys as we are people.

Let’s pause to note how remarkable this is: I have been to the zoo. To me, all the monkeys there just look like monkeys. But infants seem to see their faces with the same richness and distinctness with which I see the faces of the other people in the café I’m sitting in.

Babies soon lose this skill: By 9 months, like adults, they’re no good at all at telling apart monkeys. That’s because as time passes, infants are able to see only what they already see in the world. This is a phenomenon called “perceptual narrowing” and it is best known for its effect on language acquisition: Very early on, infants stop being able to tell the difference between certain speech sounds that they’re not hearing. We have to hear these phonemes to know them. And we have to see the monkeys to know them, too. (This works the other way too: Monkeys exposed only to human faces prefer human faces.)

This affects how we see other humans, too. My wife, studying in Nanjing at a time when there were very few white people in Nanjing, had her fairly cosmopolitan Chinese roommate ask her, “How do you people tell each other apart? You all just look the same.” She wasn’t being rude; she was genuinely bewildered. Hilariously, when my wife returned to New York, she kept mistaking people on the street for people she knew. And then she thought, My roommate was right: All white people really do look the same. After a year of just seeing Chinese faces, she was, at least temporarily, no longer able to differentiate non-Chinese faces. Of course, this is famously the case with Americans who never leave America, too: Hence, all [insert ethnicity here] look the same. This isn’t racism. It’s just perceptual narrowing. And it happens fast: At birth newborns don’t prefer faces of their own ethnicity; at 3 months, they do.

Sadly, the science suggests that my youngest, who just turned 11 months, now has eyes only for humans. When I take him to the zoo, he sees other primates the same way I do: As other. It’s my fault. If I had the first year of his life back, I’d do my best to have more macaques around the house.

Through face-to-face engagement, babies learn what to laugh at and when it makes sense to laugh.

Photo by Dereje Belachew/iStockphoto/Thinkstock

An infant’s first laugh is among the most intoxicating moments in parenting. When each of my sons laughed for the first time, I felt like they’d come to life all over again. I felt like Descartes: It laughs; therefore it is. And then I reminded myself to stop calling the baby it.

If you are the sort of parent who overthinks things—and would you be reading this if you were not?—that first laugh is shadowed by a lot of questions: Why does he know that is funny? How does he even know what funny is? And is there something stuck in my teeth?

For a long time, there were no good answers to any of these questions except the latter. (There wasn’t. I checked.) Humor was conceptualized as taking place at a higher mental level, a level to which infants had not yet ascended. But that left a stubborn problem: No one had bothered to explain why babies kept laughing.

It turns out they are laughing at you. And with you. Thinking of humor in structural, analytical terms deprives us of understanding what babies can do: They may not understand the joke, but they can share in this glorious feeling of funniness. Laughter in infancy, as Vasudevi Reddy, a psychologist at University of Portsmouth in England, has argued, seems to be an “intrinsically social, even interpersonal” act.

Remarkably, even without any deeper conception of why a grown-up might find something funny, the laughter of babies has the same characteristics as adult laughter. Like us, they laugh at many different things, in many different ways, but they often laugh in the same way at the same sort of thing. When the baby in our house laughs, I almost always know why. This is what nearly all parents report, Reddy says. Laughter isn’t a mysterious sound. It seems to bubble up from a deep and early engagement in the social world. (In contrast, and very poignantly, autistic children laugh a lot—but what they are laughing about is often opaque, even to their parents.)

The very first laughs, at around 3–4 months of age, seem to be smiles that grew too big for the face: They erupt in sound. In Baby Meets World, I write about the science of smiling, the way that social smiles build on each other, crescendoing in meaning and magnitude. Laughter works in much the same way. Through face-to-face engagement, we teach our babies what to laugh at and when it makes sense to laugh. Through parent interviews and close observation of infants, Reddy has documented that this sort of social back-and-forth is the source of almost all early laughter. Even when babies laugh from tickling, or from someone blowing on their belly, it is the social stimulation—the imagonnagetchu—that sparks the laugh as much as the physical stimuli.

Babies are keenly perceptive of silliness and playfulness. “If you can distinguish the serious and the playful,” Reddy says, “at least you’re part of the way towards understanding this person understands that funny face to be funny rather than this person has just gone nuts. Or this person has an odd face.” That’s what enables babies, from an oddly early age, to be connoisseurs of slapstick.

Within several months after his first laughs, your baby wants to make you laugh—and he won’t wait until he can tell jokes. After 8 months, infants begin to display what Reddy calls clowning—they explicitly try to get someone else to laugh. They don’t have the idea first, but they instantly catch on to the idea that something might be funny. “It starts in very simple things,” Reddy says. “You’re laughing because they’re splashing you, so they splash you some more. And the things they do to make you laugh become subtler and more clever and more sophisticated.” In Reddy’s book How Infants Know Minds, she recounts the story of an 11-month-old who imitated her great-grandmother’s snoring face—and then, after everyone laughed, did it again, and then again, “deliberately, waiting for a response.” She kept doing it for days. Like any good comedian, Reddy writes, she used what works, and for her, as for many of us, the experience of getting other people to laugh was addictive. “Funniness,” Reddy concludes, “exists only in relation.”

Reddy’s work represents a challenge to the conventions of developmental psychology. She believes that the orthodox way of studying babies—carefully staged experiments in a laboratory—is counterproductive. “Psychological phenomena are fundamentally relational,” she says, and if you study babies in a laboratory, you have removed the infant from the social world. “You’re damaging the very thing that you want to study. And some of these things, especially in development, can be a bit fragile.” She argues that psychologists need to engage with infants in order to understand them. This idea is worth dwelling on because it has implications beyond the internecine disputes of academia. It suggests that parents, the people who are actually engaged with babies most of the time, have a uniquely valuable perspective. Reddy knows this well: Almost all of her research began with observations of her own children. As infants, they did things she thought they couldn’t possibly do—they teased, or clowned, or were coy. But they could do those things. And they did.

“Parents have access to experience and information which scientists would die for,” Reddy says. “You have so much data, if you’re looking for it—you know the history, you know the background, you know that this can’t be chance, you know that this is chance—whereas with experimental situations, your conclusions are much more risky. You don’t know the backgrounds of the kids; you don’t know their development. You don’t know what happened last week.”

Of course, the danger is that the parent is biased—that their observations can’t be trusted. But Reddy says the key is that parents and scientists can see different things—and they can miss different things. Their perspectives should be seen as complementary. But too often they aren’t. “We tend not to take the participants in everyday life seriously when they talk about everyday life phenomena,” Reddy says. “It’s kind of like we don’t trust people who are in this up to their elbows.”

But sometimes it is only the people who are up to their elbows in it who can interpret what’s going on. Being emotionally engaged can be what makes babies—these mysterious creatures who stubbornly refuse to explain what they’re doing—explicable.

Reddy is unorthodox, but she is not alone in valuing what parents see. This happened to come up a few weeks ago, when I spoke with the psychologist Malinda Carpenter about pointing. Carpenter is brilliant at experiment design; her insights into pointing have come from carefully calibrated experiments. (And her theory about how and when babies “know” minds is very different from Reddy’s.) She doesn’t know exactly why babies begin to point when they do, though. And I have a baby who’s about to begin pointing. This fact did not escape her. “If you have any hypothesis about why he starts pointing when he does, I’d love to hear it,” she said. I started laughing. “No,” she said, “seriously.”

Whether babies should or should not be carried does not seem like an especially tricky question. (Sample answer: Why not? Seems to work!) It does not seem like a subject that people could spent millennia coming to radically different conclusions about. But they have!

These days, the newer the baby, the more likely we are to carry it. (For good reason.) But the ancient Greek physician Soranus thought that babies, especially boys, should not be carrieduntil four months of age. Carrying posed the risk of severe testicular injury, Soranus thought. Today we worry about raising children who aren’t well-adjusted; the Greeks worried about raising children who weren’t eunuchs. This bias against carrying held through medieval times, apparently.

Meanwhile, at the same time Soranus pronounced this, the many hunter-and-gatherer societies south of him in Africa were obliviously carrying their infants. They’d never done anything but carry their infants. There is some logic here; the anthropologist John Whiting established that infants in cold climates are more likely to be swaddled and put down in a cradle, while those in hot climates are more likely to be carried in a sling. But once we could control the temperature indoors, we had no clue what to do: In this country, for the first half of the 20th century, the medical consensus was something like, “Carry your child? Why are you even touching your child?” (I exaggerate only slightly; this was an era when experts were telling parents not to kiss their babies.) The sudden popularity of slings, beginning in the 1970s, was a radical reversal. It pulped decades of childrearing wisdom.

If you take the long view—the really, really long view—all this indecision dates back to a pivot point in human development. As I write in Baby Meets World, our hominid ancestors carried their infants without trying—that was the advantage of hairy bodies and an opposable toe. When they lost both, they squandered an extremely efficient method of child care. Suddenly, parents had to think about what to do with this helpless creature. (Those parents were pretty clever: They invented slings.) In a sense, the search for a decent daycare began with the moment, millions of years ago, that those hominid infants no longer stuck to their parents.

It’s always tempting to see the present as the final point in a journey—that we have corrected the mistakes of the past. We now understand that babies have basic socio-emotional needs; we let ourselves pick up our babies; we carry them when they want to be carried. But answers to the most basic childrearing questions tend to see-saw wildly: Chances are that in the far future, someone will read about your Ergo with abject horror.

Whether they will assume that the Ergo turned all baby boys into eunuchs—that’s another question entirely.

A Maasai woman carries her baby in Kisokon village, Kenya, in September 2008.

Photo by Radu Sigheti/Reuters

For most of history, taking care of an infant has been a constant war against body functions. All victories were temporary, contingent. In the end, the excrement always wins.

For us consumerist moderns, this huge problem hardly seems like a problem: We have intricately spun plastic fibres that can soak up a seemingly endless stream of urine. You can wait to change the diaper until it threatens to outweigh the infant. But for centuries, diapers didn’t absorb the moisture so much as trap it. In swaddling cultures, the swaddling itself was far more cumbersome and complicated and rigorous than it is today. This compounded the problem: Once you’d swaddled an infant, you really didn’t want to undo the wrapping 10 minutes later just because the child went again. In Colonial America, it has been said that “most babies spent much of their first few months wrapped tightly in wet and soiled swaddling bands.”

Even aside from very early toilet-training, the solutions of many traditional cultures were often far more clever. The Chuckchi, who live in far eastern Russia, carried their babies in fur bags with flaps filled with dry moss. When the child cried, you changed the moss. As the Norwegian Harald Sverdrup observed in his 1938 book Among the Tundra People, “A young Chukchi wife who is expecting a baby does not collect strange baby things and fine dresses with lace on them; she collects a big sack full of moss, picks all the twigs and stones out of it, and dries it well. If she has been industrious, she has all the baby things she needs, and diaper-washing is no problem.” Even Mitt Romney could have handled changing these diapers: You took out the old moss and put in new moss.

In parts of northern China, infants were encased in sandbags, which was both diaper and baby sitter. The Navajo shredded the bark of the cliffrose shrub and stuffed it between a baby’s legs on the cradleboard. These solutions were ingenious but not without problems: In Siberia, when the moss froze, it sometimes froze to the baby.

But my favorite example is from Central Asia, where some cradleboards apparently had built-in “urine tubes.” According to a detailed description of the Kurdish version, infants were tightly swaddled with the softly wrapped wooden tube (“for a male child there is a circular opening at the head of the pipe, if for a female, an oval one”) held snugly in place. The end of the tube fit into a hole in the cradleboard’s base: In the winter, a bottle was placed under it; in the summer, the urine flowed right onto the floor.

If you are compiling a baby registry right now, look no further.

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Nicholas Day's book on the science and history of infancy, Baby Meets World, from which part of this post was taken, will be published in April. His website is nicholasday.net.

Parenthood in early infancy is equal parts tedium and astonishment. The trick is telling the two apart.

This is harder than you might think. Pointing, for example, is not an obviously astonishing act. I have already pointed several times today and no one was astonished. But when a baby points ecstatically at a puppy, or responds to someone else pointing at that puppy, we should marvel at him: We have just witnessed an astonishingly complex act. In fact, by pointing, that baby is, in a very real way, acting out what makes us uniquely human.